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Metal Levels in the Soils of the Sudbury Smelter Footprint

A Report To:

Safety, Health and Environment, INCO Ltd., Ontario Division,

Copper Cliff, ON. P0M 1N0

and

Falconbridge Ltd., Sudbury Smelter Business Unit,

Falconbridge, ON. P0M 1S0

Submitted: July 12, 2004

Sudbury Regional Soils Project 2 Centre for Environmental Monitoring


EXECUTIVE SUMMARY

Metals constitute a natural component of soils, with contents dependent on soil mineral

composition and geochemical history. Man has added metals to soils through atmospheric

deposition from industrial processes, or by fertilizing with manure and fertilizers in amounts

that add more metal to the soil matrix than is removed by plant uptake. Localized, strongly

enhanced metal concentrations have been created in surface soils by atmospheric deposition

in the neighbourhood of metal extraction plants.

With the release of the OMOE report describing the distribution of metals in soil and

vegetation in the Sudbury area in 2001, the need was recognized for an extensive statistically

defensible regional soil sampling programme to enable accurate delineation of any metal

loadings to the soils ecosystem from anthropogenic activities. The necessity of obtaining a

reliable estimate of pre-industrial background levels in surficial sediments was paramount so

that reasonable loading estimates to surface soils could be calculated.

This data is necessary to study the fate of, or to determine the environmental health risk

posed by, metals added to soils by atmospheric deposition or by other sources. An

understanding of the natural physicochemical processes in the soil-plant system that govern

and regulate the behaviour of their natural metal content is also necessary in estimating the

potential ecological or human health risk of anthropogenic metals in the Sudbury

environment. Crucial in the development of the understanding of these processes is

knowledge of the geological history, of the glacial history and of the soil mineralogical and

background elemental composition.

The objectives of the study described in this report are to:

• Describe the planning and sampling program the Sudbury Regional Soil Sampling

Programme;

• Document the background levels for selected metal concentrations in regional soil

parent materials extracted with Aqua Regia; and

• Document the regional distribution of selected metal concentrations in defined

depth increments for regional soil materials extracted with Aqua Regia.


This report describing the study consists of two main sections, namely:

• A detailed narrative report documenting a summary of the geology and soil

chemistry, with a summary of the data obtained during this study, with overview

maps describing the elemental distribution in both surface soils and their parent

materials. The metadata describing the individual sampling sites, together with the

analytical data for a series of elements of environmental interest are documented in

two appendices;

• An interactive electronic map and database which combines all the meta- and

chemical data in the written narrative in a friendly interactive form which can, by

following simple installation instructions, be installed on any desktop computer

data. This interactive database also contains images of all sites sampled for analysis

in study.


ACKNOWLEDGEMENTS

Many people have contributed to the data collection for, and production of, this report. In

particular we would like to acknowledge to following: Glen Watson, Bruce Conard, and Pat

Thompson from INCO Ltd together with Marc Butler and Denis Kemp from Falconbridge

Ltd., for their financial and moral support, their incredible patience and many interesting

discussions. David Pearson and Graeme Spiers from Laurentian University guided the project

from inception to completion. Field crews and laboratory assistants without whom this report

could not have been started include: Caroline Hawson, Miriam Kaliomaki, Alan Lock,

Duncan Quick, Chris Peloso, Francois Prevost, Ryan Post, Jacqueline Richard, Chantal

Rosen, Paula Takats, Dana Willson. Special thanks go to Francois Prevost for data display

and statistical analysis; Caroline Hawson for the literature review and quality control.

National Tilden and Day Aviation provided excellent field support. The Ontario Geological

Survey provided base maps and data on Quaternary materials.

Acknowledgement is also given to personnel of the Ontario Ministry of the Environment,

especially Brain McMahon and Rusty Moody. Personnel from Golders Associates, namely

Sam Gauvreau and Natalie Boudreau, provided support and discussions during the sample

design and sample collection phases. Without their collaboration approximately 25 per cent

of the study region would not have been adequately and effectively sampled.

The principal author of this report is Graeme Spiers. Caroline Hawson, as well as completing

the data quality control analyses, prepared the first draught of the review segments of the

report. Francois Prevost completed much of the statistical analyses, the maps and the

interactive display for Appendix III. Dr. David Pearson provided thoughtful insight in

reviewing the report.


TABLE OF CONTENTS

EXECUTIVE SUMMARY.................................................................................................3

ACKNOWLEDGEMENTS ...............................................................................................5

LIST OF TABLES............................................................................................................9

LIST OF FIGURES........................................................................................................11

SUDBURY REGIONAL SOILS PROJECT ...................................................................14

INTRODUCTION ...........................................................................................................14

Industrial History ...................................................................................................................15

GEOLOGY OF THE SUDBURY AREA ........................................................................16

Introduction ............................................................................................................................16

Geological Setting ...................................................................................................................16

PRECAMBRIAN GEOLOGY..............................................................................................16

QUATERNARY GEOLOGY ...............................................................................................18

Ice Flow Direction ............................................................................................................19

Till ....................................................................................................................................20

Landforms.........................................................................................................................20

Sedimentary Deposits .......................................................................................................20

PHYSIOGRAPHY OF THE SUDBURY AREA ..................................................................22

Drainage ...........................................................................................................................23

SOILS OF THE SUDBURY AREA .....................................................................................23

MINING AND SMELTING EMISSIONS............................................................................24

Metal Particulate Deposition .............................................................................................27

SOIL.....................................................................................................................................28


MINERALOGY OF SUDBURY SOILS ..............................................................................29

Silicate Minerals ...............................................................................................................30

Clay Mineralogy ...............................................................................................................31

Organic Horizons ..............................................................................................................33

SOIL CHEMISTRY..............................................................................................................34

Parent Materials ................................................................................................................34

SUDBURY SOILS ...............................................................................................................37

REGIONAL SOIL STUDIES IN THE SUDBURY AREA...................................................45

THE SUDBURY REGIONAL SOILS PROJECT.................................................................48

Regional Sampling Plan....................................................................................................48

SOIL SAMPLING PROTOCOL...........................................................................................50

Parent Material Sampling..................................................................................................53

Soil Profile Sampling ........................................................................................................54

SOIL SAMPLE PREPARATION.........................................................................................54

SAMPLE ANALYSIS ..........................................................................................................55

Quality Program................................................................................................................56

NUMERICAL ANALYSIS TECHNIQUES .........................................................................58

Cluster Analysis................................................................................................................59

Factor Analysis .................................................................................................................59

DATA PRESENTATION.....................................................................................................60

RESULTS......................................................................................................................62

Metal Distribution in Soil Profiles .........................................................................................62

Metal Distribution in Regional Parent Materials .................................................................64

Regional Geochemical Maps.............................................................................................74

Metal Correlations in Regional Parent Materials.................................................................92

Metal Distribution in Regional Surface Soils ........................................................................98

Soil Layer 0-5 cm ...........................................................................................................100

Soil Layer 5-10 cm..........................................................................................................109


Soil Layer 10-20 cm........................................................................................................116

Regional Geochemical Maps for Surface Soils ...............................................................124

Metal Correlations in Regional Surface Soil Layers...........................................................143

Metal Enrichment in Regional Soil Surface Layers............................................................144

Zonation of Metal Enrichment in the Sudbury Smelter Footprint ....................................146

RECOMMENDATIONS ...............................................................................................149

Area Sampled........................................................................................................................149

Clay Mineralogy ...................................................................................................................150

Chemical and Mineralogical Nature of Emissions ..............................................................150

Solid Phase Speciation ..........................................................................................................151

Bioavailability and/or Bioaccessibility of Metals ................................................................151

REFERENCES ............................................................................................................153


List of Tables

Table 1: Heavy metal and sulphur discharges for 2001 for Inco Limited and Falconbridge Limited. ............................................................................................................................16

Table 2: Distribution of major and trace elements in Canadian soil parent materials. ...............38

Table 3: MOE guidelines for the upper normal limit for metals in Ontario soils (from Heale, 1993)......................................................................................................................39

Table 4: Distribution of selected major and trace elements within the surface layers of selected soils at various distances from the Coniston smelter. ...........................................41

Table 5: Metal proportions in the various fractions from selected soils of the Sudbury region using the European Union extraction procedure. ....................................................42

Table 6: Distribution of selected major and trace elements within the surface layers of selected soils of the Coniston airshed. From Dudka et al., (1995). ...................................45

Table 7: Distribution of selected major and trace elements within the solum for a pedon equidistant from the Copper Cliff and Coniston smelters. The EMMA data provide total concentrations of the analyte elements within the soil samples..................................57

Table 8: Distribution of Aqua Regia extractable levels of 19 major and trace elements in parent materials of the Sudbury Smelter footprint region. .............................................66

Table 9: Pearson Correlation for the Aqua Regia extracted metals for all samples from parent materials sampled within the study region (n = 255 samples). ................................93

Table 10: Principle component analysis describing the relationship between the compositional chemistry of Aqua Regia extracted metal(loid)s in the soil parent materials of the soils of the Sudbury smelter footprint. .....................................................95

Table 11: Varimax rotated loading matrix for Aqua Regia extracted metal(loid)s in the soil parent materials of the soils of the Sudbury smelter footprint............................................96

Table 12: Summary statistics describing the Aqua Regia extractable concentrations for 20 elements in the 0 to 5 cm depth of soils within the Sudbury area. .....................................99

Table 13: Summary statistics describing the Aqua Regia extractable concentrations for 20 elements in the 5 to 10 cm depth of soils within the Sudbury area.....................................99

Table 14: Summary statistics describing the Aqua Regia extractable concentrations for 20 elements in the 10 to 20 cm depth of soils within the Sudbury area.................................100


Table 15: Pearson Correlation for the Aqua Regia extracted metal(loid)s for all samples from the 0 to 5 cm layer within the study region (n = 387 samples). ...............................144

Table 16: Mean concentration of Aqua Regia extractable metal(loids) from the individual layers of all sites sampled in the Sudbury region, along with calculated enrichment factors for the surface (0 - 5 cm) layer calculated using aluminium as an immobile element. ..........................................................................................................................146

Table 17: Mean concentration of metal(loid)s in the 0 to 5 cm layer of sampled soils within concentric zones around the Sudbury smelter region. The centre of the circular zones is at the centroid of the three smelters in the region.........................................................149


List of Figures Figure 1: Regional geology of the Sudbury area. .....................................................................17

Figure 2: Quaternary geology of the Sudbury region. ...............................................................19

Figure 3: Sampling program for the regional soil study, with sampling exclusion zones delineated..........................................................................................................................49

Figure 4: Photograph of vegetation at a representative soil sampling site..................................51

Figure 5: Typical soil sample in the Sudbury area.....................................................................52

Figure 6: Diagram illustrating the variability of horizons, horizon boundaries in undisturbed soils at forested sites. Coloured boxes indicate the difficulty in obtaining homogeneous samples of any one layer unless sampling is completed on a horizon basis. ......................53

Figure 7: Collection of a soil parent material sample with Dutch augur. ...................................54

Figure 8: Typical Podzolic pedon developed under mixed birch and coniferous vegetation in the Sudbury region. .......................................................................................................55

Figure 9: Examples of weathered aerosolic particles retained in the LFH horizons of a forested soil from the Sudbury region. ..............................................................................63

Figure 10: Distribution of aluminium in the soil parent materials of the Sudbury Region. ........75

Figure 11: Distribution of arsenic in the soil parent materials of the Sudbury Region. ..............76

Figure 12: Distribution of barium in the soil parent materials of the Sudbury Region. ..............77

Figure 13: Distribution of beryllium in the soil parent materials of the Sudbury Region...........78

Figure 14: Distribution of calcium in the soil parent materials of the Sudbury Region..............79

Figure 15: Distribution of cobalt in the soil parent materials of the Sudbury Region. ...............80

Figure 16: Distribution of chromium in the soil parent materials of the Sudbury Region. .........81

Figure 17: Distribution of copper in the soil parent materials of the Sudbury Region. ..............82

Figure 18: Distribution of iron in the soil parent materials of the Sudbury Region....................83

Figure 19: Distribution of molybdenum in the soil parent materials of the Sudbury Region. ....84

Figure 20: Distribution of magnesium in the soil parent materials of the Sudbury Region. .......85

Figure 21: Distribution of manganese in the soil parent materials of the Sudbury Region.........86


Figure 22: Distribution of nickel in the soil parent materials of the Sudbury Region. ...............87

Figure 23: Distribution of lead in the soil parent materials of the Sudbury Region. ..................88

Figure 24: Distribution of selenium in the soil parent materials of the Sudbury Region. ...........89

Figure 25: Distribution of strontium in the soil parent materials of the Sudbury Region. ..........90

Figure 26: Distribution of vanadium in the soil parent materials of the Sudbury Region...........91

Figure 27: Distribution of zinc in the soil parent materials of the Sudbury Region. ..................92

Figure 28: Distribution of aluminium in the 0-5 cm layer of soils of the Sudbury Region.......125

Figure 29: Distribution of arsenic in the 0-5 cm layer of soils of the Sudbury Region. ...........126

Figure 30: Distribution of barium in the 0-5 cm layer of soils of the Sudbury Region. ...........127

Figure 31: Distribution of beryllium in the 0-5 cm layer of soils of the Sudbury Region. .......128

Figure 32: Distribution of calcium in the 0-5 cm layer of soils of the Sudbury Region. ..........129

Figure 33: Distribution of cadmium in the 0-5 cm layer of soils of the Sudbury Region. ........130

Figure 34: Distribution of cobalt in the 0-5 cm layer of soils of the Sudbury Region. .............131

Figure 35: Distribution of chromium in the 0-5 cm layer of soils of the Sudbury Region. ......132

Figure 36: Distribution of copper in the 0-5 cm layer of soils of the Sudbury Region. ............133

Figure 37: Distribution of iron in the 0-5 cm layer of soils of the Sudbury Region. ................134

Figure 38: Distribution of magnesium in the 0-5 cm layer of soils of the Sudbury Region......135

Figure 39: Distribution of manganese in the 0-5 cm layer of soils of the Sudbury Region. .....136

Figure 40: Distribution of molybdenum in the 0-5 cm layer of soils of the Sudbury Region. ..137

Figure 41: Distribution of lead in the 0-5 cm layer of soils of the Sudbury Region. ................138

Figure 42: Distribution of nickel in the 0-5 cm layer of soils of the Sudbury Region. .............139

Figure 43: Distribution of selenium in the 0-5 cm layer of soils of the Sudbury Region. ........140

Figure 44: Distribution of strontium in the 0-5 cm layer of soils of the Sudbury Region.........141

Figure 45: Distribution of vanadium in the 0-5 cm layer of soils of the Sudbury Region. .......142

Figure 46: Distribution of zinc in the 0-5 cm layer of soils of the Sudbury Region. ................143


Figure 47: Graphs illustrating the concentrations of the individual anthropogenic metal(loid)s along a gradient form the smelter zone centroid indicate the impact of the smelter tends towards regional background approximately 120km from the heart of the Sudbury metallurgical region. .........................................................................................148


Sudbury Regional Soils Project

INTRODUCTION

Metals constitute a natural component of soils, with concentrations dependent on soil mineral

composition and geochemical history. Man has added metals to soils through atmospheric

deposition from industrial processes, or by fertilizing with manure and fertilizers in amounts

that add more metal to the soil matrix than is removed by plant uptake. Localized, strongly

enhanced metal concentrations have been created in surface soils by atmospheric deposition

in the neighbourhood of metal extraction facilities. Soils, more than any other sampling

medium, reflect the total historical metal accumulation from the point source, but modified to

varying degrees by soil forming processes and erosion.

The metals originating from anthropogenic sources in a soil do not behave differently from

the natural metal ions present. Therefore, to study the fate of, or to determine the

environmental health risk posed by, metals added to soils by atmospheric deposition or by

other sources, an understanding of the natural physicochemical processes in the soil-plant

system that govern and regulate the behaviour of their natural metal content is necessary.

Crucial in the development of the understanding of these processes is knowledge of the

geological history, of the glacial history and of the soil mineralogical and background

elemental composition.

In Sudbury, home of one of the world’s largest copper–nickel mining camps, the mining and

processing of mineral deposits for over a century has raised concern about the potentially

high levels of heavy metals in the soil environment. Identification of chemical contamination

of Sudbury soils thus requires an understanding of the natural processes involved in the

formation of the regional soils, of the inherent heavy metal content of underlying rock units,

of the potential increased metal content of surficial materials through mineralizing processes.

The anthropogenic processes, such as mining and smelting, have released metal-rich aerosols

that have been washed from the atmosphere by meteorological events to be deposited on the

landscape surface. Locally, leaching of heavy metals from rock piles and tailings ponds,

together with fugitive emissions from ground sources and smelter sites, may prove

significant.


The Sudbury Regional Soils Project is a sampling, analytical and interpretative program

designed to provide detailed information describing metal levels in parent materials and soils

within the footprint of the Sudbury smelter region as a pre-requisite to the initiation and

development of one of the largest and comprehensive ecological and human risk assessment

projects ever completed on this sensitive planet.

Industrial History

The first industry in the Sudbury area developed around the rich forests (Gunn, 1995). After

the great fire of Chicago in 1871, Sudbury area lumber helped rebuild the city. The

transcontinental railway development also put demands on the local forests because of the

need for railway ties and trestles. Denudation of the forests resulted in the faster spread of

man made and natural fires. Lumbering remained dominant until the 1920s (Winterhalder,

1995). A major consequence of the increased acreage being felled was an increase in regional

soil erosion, especially on the shallow soils of the steeper slopes.

The first Cu-Ni discovery was made in 1856 (Murray, 1857). The Canadian Copper

Company commenced production at Copper Cliff in 1886 at the Murray Mine, discovered in

1883. Heap roasting began the same year. Although several companies have been involved in

the development of the Sudbury mining camp, there are now only two producers,

Falconbridge Limited and INCO Limited. Peak production occurred in 1974 when 209,000

tonnes of nickel were produced, decreasing to 128,558 tonnes of nickel (21% of the world’s

nickel production) in 1988. In 2000 Sudbury operations for the two companies produced

113,945 tonnes nickel and 301,987 tonnes copper (MNDM Information and Marketing

Services Section, unpublished data, 2002).

Smelter emissions from Sudbury area smelters have decreased dramatically from their

maximum in the late 1960s. In 1995 total SO2 emitted from the INCO and Falconbridge

smelters was 281,000 tonnes; the Residual Discharge Information System (Environment

Canada, unpublished data, 1995) places the total of suspended particulate matter discharged

to the atmosphere for the INCO Copper Cliff smelter at 7050 tonnes per year and for the

Falconbridge smelter 1180 tonnes per year (Table 1). The data in Table 1 are from National

Pollution Release Inventory 2002 (Environment Canada, unpublished data, 2002).


Table 1: Heavy metal and sulphur discharges for 2001 for Inco Limited and Falconbridge Limited.

Location Cu Zn Ni Pb Cd As H2SO4 H2S

tonnes

Inco Central Mills 37.76 3.84 195.80 0.91 0.36 0.12 27.26 --

Copper Cliff Nickel Refinery

5.98 -- 12.42 6.68 -- 3.94 -- --

Copper Cliff Smelter Complex

109.64 18.96 64.19 63.40 4.84 52.91 1271.08 --

Inco Copper Refinery 43.42 1.20 0.50 2.92 0.05 2.54 0.99 --

Falconbridge Smelter 10.66 5.32 11081 6.24 1.70 0.27 24.87 21.20

NB: Data from National Pollution Release Inventory 2002 (Environment Canada, unpublished data, 2002).

GEOLOGY OF THE SUDBURY AREA

Introduction

This overview places Sudbury soils into a regional geological context. The geology and

chemistry of the bedrock, the Quaternary history, and especially the provenance,

transportation and metal chemistry of the glacial units are summarized. These processes

influence soil chemistry and generate the normal background levels of individual elements.

Knowledge of this background data enables a review of the chemical composition of the soils

to ascertain the presence and level of anthropogenic contamination. A synopsis of previous

soil regional published and unpublished soil studies, with an emphasis on limitations of the

analytical methods used, is presented. Limited analytical data for vegetation and dustfall-

rainfall-snowfall processes is also reviewed.

Geological Setting

PRECAMBRIAN GEOLOGY

The Sudbury Structure (Figure 1) is an elliptical unit produced by a meteorite colliding with

the southern part of the Superior Province at 1.85 Ga. The impact melted rocks to form the

world’s largest impact-related melt sheet. The melt sheet of Sudbury Igneous Complex is

composed, from base to top, of norite, quartz gabbro and granophyre. Above the Sudbury

Igneous Complex is the Whitewater Group composed from base to top of the Onaping,

Onwatin and Chelmsford formations. The Onaping Formation is a series of fallback breccias


Figure 1: Regional geology of the Sudbury area.

overlain by Chelmsford and Onwatin formations. The Onaping Formation represents impact-

related volcanism.

Two major, cross cutting types of breccia are present 1) Sudbury Breccia and 2) Footwall

Breccia. Sudbury Breccia is a heteolithic breccia forming bodies from several metres to

kilometres in size that cross cut all pre-impact units up to 80 km from the Sudbury Igneous

Complex. Footwall Breccia occurs along the contact between the Sudbury Igneous Complex

and country rocks and in both radial and concentric “offset dikes”. This latter breccia unit

consists of quartz diorite and various other Sudbury Igneous rock types and is host to most of


the Sudbury ore bodies, both where it is subjacent to the Sudbury Igneous Complex and in

“offset dikes”. As host to the ore deposits, its mineralogy and geochemistry are important in

discriminating between anthropogenic contamination and influences of bedrock in the

geochemistry of soils. Note an endogenic origin has also been proposed for the origin of the

Sudbury Igneous Complex (Muir, 1984). The Sudbury Igneous Complex has been divided

into the Main Mass (norite, quartz gabbro, and granophyre) and Sublayer (Contact Sublayer

and Offset Sublayer) (Dressler et al., 1991). Mineralization of importance occurs in the

sublayer and the offset dikes.

QUATERNARY GEOLOGY

Quaternary and minor Holocene deposits form the soil parent material of the Sudbury region

(Figure 2). An understanding of these deposits is therefore important in any interpretation of

soil geochemistry. Quaternary deposits and features preserved within the Sudbury area are

almost certainly Wisconsinan. Tills found in the area likely correlate to the Adam Till of the

Hudson Bay Lowland (Skinner, 1973) and the Matheson Till of the Timmins and Kirkland

Lake areas (Hughes, 1959, 1965). No nonglacial sediments attributed to the last interglacial

period occur in the Sudbury area (Barnett and Bajc, 2002).

The Laurentide Ice Sheet covered Ontario, extending into the northern United States of

America about 20,000 years ago. This ice sheet had three main centres of growth: 1) the

interior uplands of Labrador and Quebec, 2) the Keewatin area in the Northwest Territories

and 3) Baffin Island. Ice of the Labrador Sector covered the Sudbury area and generally

flowed to the south-southwest (Boissoneau, 1968). Boissoneau (1968) describes an eastern

lobe that flowed southwest and a western lobe that flowed more southerly both meeting near

Sudbury.

During deglaciation, glacial lakes formed against the receding ice margin within the Great

Lakes Basin. Glacial Lake Algonquin occupied the Lake Huron, Lake Michigan and part of

the Lake Superior basins including the Sudbury area (Barnett and Bajc, 2002). Deglaciation

of the Sudbury area occurred 10,500 to 10,000 years ago. There is much evidence of the

glaciation, ranging from striae on bedrock to kilometre-scale roche moutonées and


whalebacks, to large erratic, far-travelled boulders littering the surface and many stony soils,

attesting to the presence of continental glaciers.

Figure 2: Quaternary geology of the Sudbury region.

Ice Flow Direction

Ice-flow directional indicators define an ice-flow pattern that was strongly influenced by

regional topography. Ice-flow across the Abitibi Uplands and the north edge of the Sudbury

Basin was north to south (170º to 210º). Within the Valley, a shift in flow was recorded at

between 220º and 245º. South of the Sudbury Basin, ice flowed at 205º to 225º. Evidence of

an earlier ice flow event is recorded along the north rim; however, the magnitude of glacial

dispersal associated with this older event is not known (Barnett and Bajc, 2002).


Till

Till is “sediment deposited directly by a glacier with little or no subsequent reworking”

(Dreimanis, 1988). There are two main types of till 1) subglacial till deposited by lodgement

and melt-out processes and 2) supraglacial tills deposited by flow from the upper surface of

glaciers. Debris within the glacier can move between the various transport zones (Barnett,

1992). Tills are poorly sorted, sheet-like deposits that contain clay to boulder sized particles.

Till appears massive but may contain discontinuous lenses or layers of stratified sediment.

Landforms

Landforms created by a continental ice sheet influence pedological development. Landforms

include: 1) linear features parallel to flow, 2) linear features transverse to flow and 3)

features lacking consistent orientation. Linear features formed parallel to ice-flow include

drumlins, crag-and-tail features and interlobate moraines. Linear features that form

transverse to ice flow include Rogen and de Geer moraines. Landforms lacking in orientation

are ground moraine and hummocky ground moraine (Barnett, 1992) are common in the

Sudbury region.

Sedimentary Deposits

Sediments deposited from glacial meltwater streams form glaciofluvial sediments, which are

sorted, stratified gravel and/or sand. As a result of being deposited in contact with the

glacier, abrupt changes in grain size and stratification occur vertically and laterally.

Glaciofluvial outwash deposits are generally more consistent laterally and tend to become

finer grained in a down-flow direction (Barnett and Bajc, 2002). Glaciolacustrine deposits

are commonly stratified sediments deposited directly from the glacier into a standing body of

water. Coarse-grained glaciolacustrine sediments of sand and gravel form beaches, deltas and

subaqueous fans. Fine-grained glaciolacustrine sediments, silt and clay, are deposited in

deeper water basinal settings. The dominant depositional environments for glacial sediments

in the Sudbury area are: the subglacial environment, the proglacial lake, and braided streams.

There are many erosional features on the bedrock of the Sudbury area; these were produced

by abrasion due to the dragging of glacial debris at the base of a glacier and/or by plucking

as a result of pressure gradients. Subglacial meltwater also modified the bedrock surface by


aiding the plucking process and sculpting the bedrock surface leaving a suite of elaborate

erosional forms.

Till forms the most widespread glacial sediment in the Sudbury area, forming a thin

discontinuous layer above bedrock (


Although glacial deposits are generally thin and discontinuous within the Sudbury Basin

(Barnett and Bajc, 2002), isolated areas with thicknesses of 120 m are reported (Burwasser,

1979). In the rock dominated Abitibi Uplands, Penokean Hills and the Cobalt Plain,

Quaternary sediments are thin (


about 40 m over 39 km (Barnett and Bajc, 2002). Local relief in the Valley is about 15 m and

in places as much as 30 m. Some bedrock ridges reach 320 m above sea level

Drainage

The Sudbury area is drained southward by rivers and streams that flow into Georgian Bay

(Pearson et al., 2002). Most of the region is drained by the Spanish River in the west; the

French River in the east drains a small part of the region. The river courses are largely

bedrock controlled, although the Vermillion River where it cuts unconsolidated sediments of

the Sudbury Basin has well developed meander patterns. Surface drainage influences

transportation of glacial material and contaminated materials from tailings ponds, ore heaps

and other industrial sites. Pearson et al., (2002) have produced a watershed map of the region

from which it is possible to deduce the probable path of any surface runoff.

SOILS OF THE SUDBURY AREA

The characteristics of soil are greatly influenced by the nature of the parent material, together

weathering and erosion processes. The soil mineralogical and chemical composition in the

Sudbury area will, therefore, reflect the bedrock geology of the region, the up-ice geology,

the organic input from the flora and fauna of the region, and exogenous materials such as

particulate matter from both long and short-range transport processes. Sudbury area soils

belong to five orders of the Canadian Soil Classification System (Agriculture Canada Expert

Committee on Soi1 Survey, 1987): Luvisolic, Gleysolic, Podzolic, Brunisolic, and Organic

(Gillespie et al., 1983).

Luvisolic soils occur on calcareous or high base status soil parent materials. They have

light coloured eluvial horizons and an illuvial B-horizon in which silicate clay has

accumulated. Luvisols develop in well to imperfectly drained sites on sandy loam to clay

textured parent materials under forest vegetation. Luvisols of the Sudbury area belong to

the Gray Luvisol Great Group, due primarily to the effect of climate and parent material on

soil development. These soils have developed on glaciolacustrine sediments.

Gleysols are poorly drained and their profile is indicative of long periods of water

saturation and reducing conditions. Two groups of Gleysols are described in this area 1)


Humic Gleysols with a high base status and a thick organic rich Ah horizon underlain by a

gleyed mottled Bg or Cg horizon; 2) Gleysol Great Group developed on mineral soils of

low base status. The Ahg horizon is either absent or less than 10 cm thick. These soils have

commonly developed on glaciolacustrine, glaciofluvial or fluvial sediments.

Podzols occur in coarse to medium textured low-base parent materials under forest or heath

vegetation in cool to very cold humid to perhumid climates. Podzolic soils can also develop

in strongly leached calcareous materials.

Brunisols exhibit a lack of horizon development compared to the other soils groups. The

two Brunisols mapped in the Sudbury area are Melanic Brunisols and Sombric Brunisols.

Melanic Brunisols have a high base status and develop on calcareous parent materials,

whereas Sombric Brunisols have a relatively low base saturation. These soils commonly

form on coarser textured morainal and outwash parent materials

Organic soils have developed from organic deposits of mosses, reeds, or woody vegetation.

The three groups recognized in the area are Fibrisol, Mesisol and Humisol depending on

the degree of decomposition of the organic material. Organic soils are commonly found in

enclosed basins, or on the margins of lake basins.

As the focus of this study was on well to imperfectly drained soils developed on the regional

glaciogenic sediments, the organic or wetland soils were not sampled in this study. However,

as the ombrotrophic peat soils are only fed by atmospheric sources, these organic soils are

excellent archives of historical aerosolic inputs (Shotyk et al., 2000, 2001, 2002; Zoltai,

1988) that must be critically sampled and studied to enable currently non-available emissions

histories to be reconstructed.

MINING AND SMELTING EMISSIONS

Sudbury has been home to mining, smelting and refining of nickel-copper ores since the late

nineteenth century. The early methods of refining included the use of roast beds, and later,

roast yards. Layering sulphide ore with locally cut timber that was then ignited to heat the

ore until the sulphide minerals ignited formed the roast beds. The resultant nickel and copper

concentrates were gathered for further refining (Winterhalder, 1995). The roasting process


generated dense plumes of smoke, including sulphur dioxide (Freedman and Hutchinson,

1980). Thus the local forests were denuded by felling for use as fuel and for construction of

the railway, and also by the noxious gases emanating from the roast beds. Rapid, severe

erosion of the barren soils ensued, resulting in exposure of the bedrock that has, in turn, been

subject to intense acid weathering.

Estimates suggest that as much as 2.7 x 105 tonnes of SO2 were emitted annually, together

with many tonnes of heavy metal particulates (Holloway, 1917), at the peak of the ore roast

yard era between about 1895 and 1928. In 1928 the use of open roast beds was forbidden by

an order from the Ontario Legislature. The open roast beds were supplemented with more

efficient smelter facilities with smoke stacks. The three smelters in the Sudbury region were

located at Copper Cliff, Coniston and Falconbridge. In the mid 1970s, Ni and Cu emissions

from the three smelters were estimated at 1100 tonnes per year (Cox and Hutchinson, 1981).

The Coniston Smelter was decommissioned in 1972 when the “Super Stack” (381 m) was

brought on line at INCO Limited’s Copper Cliff smelter. Today all smelting in the region is

carried out at the Copper Cliff (INCO Limited) or Falconbridge (Falconbridge Limited)

smelter. The INCO stack emitted 1.1 x 106 tonnes of SO2 and 1.2 x 106 tonnes in 1977

(Freedman and Hutchinson, 1980). This represented a reduction from the 2.5 x 106 tonnes

reported in 1970. Emissions from the Falconbridge smelter totaled approximately 2.0 x 105

tonnes in 1977, about 17% of the Copper Cliff total (Freedman and Hutchinson, 1980). In

1976 Total Canadian SO2 emissions were 6.0 x 106 tonnes (Air Pollution Control Directorate,

1976), with emissions from the Sudbury area representing about 25% of the national

inventory.

In addition to sulphur-rich emissions, large quantities of metal-containing particulate

materials are vented through the stacks. In 1976 and 1977 emissions from the Copper Cliff

stack amounted to 1.0 x 104 tonnes, a reduction from the total INCO emissions of 3.4 x 104

tonnes in 1970 (Freedman and Hutchinson, 1980). The particulate material emitted primarily

comprises of iron oxides, with significant amounts of nickel and copper emissions. The

majority of the particulates sampled were less than 7 m as the Cotrell dust collectors in use

at the Copper Cliff smelter did not efficiently trap these small particles (Freedman and

Hutchinson, 1980). Total Canadian emissions for all particulates in 1972 were 2.12 x 106


tonnes with 1.42 x 106 tonnes originating from industrial processes (Air Pollution Control

Directorate, 1976). Thus, particulate emissions from the Copper Cliff smelter complex

account for approximately 0.5% of the total Canadian emissions from all sources.

Smelter emissions from the Sudbury area smelters have decreased over the years. In 1995

total SO2 emitted from the INCO Copper Cliff and the Falconbridge smelters totaled 281,000

tonnes per year. Annual metal emissions, in 1995, were approximately; 140 tonnes Cu, 10

tonnes Zn, 87 tonnes Ni, 52 tonnes Pb, 10 tonnes Cd, and 48 tonnes As (Air Pollution

Control Directorate, 1976). The Residual Discharge Information System (Ministry of

Environment, unpublished data, 1995) places the annual total of suspended particulate matter

emitted to the atmosphere for the Copper Cliff smelter at 7050 tonnes and for the

Falconbridge smelter 1180 tonnes. The 2001 data for the INCO and Falconbridge operations

in Sudbury are presented in Table 1.

The amount of trace elements released during smelter operations is a function several factors.

These factors include the mineralogy of the ores being processed, the tonnage processed, the

temperature of the smelting process, with the more volatile elements (e.g., As, Cd, Hg, Pb,

Sb, Se, Tl, Zn) emitted at lower temperatures than the less volatile elements (e.g., Cu, Fe,

Mn, Ni), and the efficiency of the emission control equipment at the facility (e.g., multi-

cyclones, electrostatic precipitators or bag houses).

Although there is limited data on the size of particles released, the particulate matter released

by the INCO smelter is dominantly fine grained (80% by mass) with particles 2 m

(Environment Canada, unpublished data, 1999). Metals such as Cu and Ni may be primarily

associated with coarse particle sizes (>2.5 m) with mass median diameters


Regional rainfall contains both particulate and soluble phase emissions from smelting

operations. Rainfall close to the smelters in the Sudbury region is acidic, containing high

levels of soluble metallic ions. In 1970 the conductivity of rainwater collected 1.6 km from

the Coniston smelter was 450 mhos and at 13.5 km was still 64 mhos. The fallout of Ni

dissolved in rainwater decreased from 271 m g-2 month-1 at 1.6 km to 8.1 m g-2 month-1 at,

19.3 km (Cox, 1975).

Snow sampling provides a means of examining deposition over the duration of the winter

period of elements of interest. Snow sampling in the Sudbury area was carried out in 1972

(McGovern and Balsillie, 1973), with samples being analyzed for total S, Cd, Cl, Co, Cu, Fe,

Ni, Zn and pH. Three sets of samples were collected 1) after significant snowfall in January

and 2) February and 3) during freeze-thaw in April. The values for April were significantly

lower than the other two sets of samples, suggesting that metals were removed by run-off to

regional lakes, streams or groundwaters, or they percolated or leached out during the thaw.

Levels of all elements except Cl decreased with increasing distance from Sudbury, indicative

of the influence of smelting operations on regional precipitation chemistry.

Metal Particulate Deposition

Metals, deposited from the atmosphere by wet and dry depositional processes, can

accumulate in a variety of environmental media including soil, water and sediment.

Concentrations of emitted metals typically decrease exponentially with distance from the

source. Particulate matter is generally subdivided into a fine fraction (2.5 m). Particulate matter may be primary or secondary. Primary particulate

matter is emitted directly into the atmosphere, whereas secondary is formed in the

atmosphere through chemical and physical transformations. The principal gases involved in

secondary particulate formation include SO2, NOx, volatile organic compounds and NH3.

Primary particles are present in both the coarse and fine fractions, while secondary particles

are dominantly in the respirable fine fraction. Particulate matter may include elemental and

organic carbon compounds, aluminium, iron and silicon oxides, trace metal rich spheres,

metal sulphates, and metal nitrates.


Extremely fine particles (


This biodynamic accumulation of metals (van Tilbourg, 1998) supports the suggestion by

Bohn et al., (2001) that normal concentration of Ni and Cu in surface soils can range from 10

to 1000 mg kg-1 and 2 to 100 mg kg-1. Complexation by soluble organic anions increases the

concentration of Cu and Zn in the surface soil.

Natural levels of metals in soils are in equilibrium with the inorganic and organic

components of a soil. Due to soil processes, these metals are not biologically available. This

is also valid for metals added to soils, given time to reach the same equilibrium position.

Time decreases the availability of ions added to soils. Recent experiments have shown, for

example, that the ecotoxicity of added zinc decreases with time (Smit, 1997) as the applied

zinc becomes incorporated in soil organic matter or soil secondary minerals. Time allows

ions to diffuse through the soil solution to the strongest sorptive sites on weathered soil

particles (Bohn et al., 2001). Time leads to the aging of soil solids, with smaller reactive

phases evolving into larger, less reactive phases and less plant-available phases. Leaching of

toxic ions through the solum is generally negligible in undisturbed sites. Potentially toxic

elements generally remain within a few centimetres of where they first come into contact

with the soil matrix unless stirred by cultivation. If retained at the immediate soil surface,

they may be above the active portion of the root zone and may, therefore, be relatively

unavailable to plants unless active acidic dissolution processes are dominant.

MINERALOGY OF SUDBURY SOILS

Minerals formed by igneous or metamorphic processes are commonly unstable at the surface

of the Earth. The minerals undergo weathering, with the products being re-equilibrated with

the current dynamic system. The Precambrian bedrock, in this area, is above global

background levels in nickel and copper in sulphide minerals that are the major ore minerals;

also as trace elements in silicate minerals, for example, olivine and pyroxene, and the oxide

minerals, for example, magnetite (Deer et al., 1966). Copper is an incompatible element with

a partition coefficient of 1.0 for the

same minerals (Rollinson, 1993; Earthref, 2002). Hosted within the silicate mineral phases of

the Quaternary sediments forming the parent materials of the region will also be immiscible

mineral phases such as blebs of sulphide minerals (Sposito, 1989).


There is minimal information in the open literature on Sudbury soils describing relict silicate

mineralogy, clay mineralogy, and soil solution composition (Costescu and Hutchinson, 1972;

McGovern and Balsillie, 1973; Whitby and Hutchinson, 1974; Cox, 1975; Dreisinger, 1976;

Dreisinger and Buchannan, 1977, 1979; Dreisinger, 1978; Rutherford and Bray, 1979;

Hazlett et al., 1983; Taylor and Crowder, 1983; Chan and Lusis, 1986; Negusanti and

McIlveen, 1990; Heale, 1993; Dudka et al., 1995, 1996; Gundermann and Hutchinson, 1995;

Adamo et al., 1996; Chuan et al., 1996; Dudka and Adriano, 1997; Bajc and Hall, 2000;

Morra and McIlveen, 2001; Adamo et al., 2002). Therefore, speculation about the

bioavailability of metals is difficult. Metals within the lattice of resistant minerals are not

readily available for uptake by biologic processes whereas heavy minerals absorbed on clay

minerals are more readily available, whilst those existing as either free ions or ionic

complexes in the soil solution are perhaps most readily bioavailable (Sposito, 1989). There

is, however, a voluminous literature on the bedrock geology and mineralogy of the area (Pye

et al., 1984; Lightfoot and Naldrett, 1994).

Silicate Minerals

Adamo et al., (2002) used scanning electron microscopy and energy dispersive spectroscopy

(SEM/EDS) for the analysis on iron oxides and sulphides in the soil, both before and after

sequential extractions. They observed the results of incomplete dissolution of the mineral

phases at the second and third stages of the sequential extraction. Microchemical analysis

indicated the presence of Ni, Cu and Zn in some of the particles along with Al, Si, K, Ca,

Mn, Fe, ±Zr and ±S. In the fine sand fraction Adamo et al., (1996) observed numerous

spherical particles containing encapsulated Fe and Ni metallic or oxide phases in a matrix

rich in Si, Ca, and Fe. These particles were formed from molten materials during the

smelting process, and were deposited on the sampled soils following emission from the

regional smelters. Hollow spheres containing particles rich in Cu and S, with smaller

amounts of Fe and Ni, were also observed. Trace amounts of Cu and Ni were observed in the

clay fraction (Adamo et al., 1996). Elemental maps of crushed soil materials indicated that

Cu to be diffused throughout the soil matrix, whereas Ni was concentrated in zones. These

researchers did not attempt to identify the specific minerals species by X-ray diffraction.


The residue remaining from the sequential leaching experiments contained silicate and clay

minerals, as well as Fe containing micro-aggregates. These micro-aggregates sometimes also

contained P, Cu and Ni, with isolated 20-40 m diameter framboids of pyrite also being

identified. Hollow spherical particles were found to exist in the residue from the sequential

leaching experiments. The residue, after “total digestion”, contained particles with C and S

contents, as well as measurable concentrations of Si, Al, Fe, Ca, Ti, Zr, Cr, ±Mg, ±K, ±Ni,

and ±Cu. These particles were insoluble in HF (Adamo et al., 1996). Adamo et al., (1996)

found Cu to be more readily extractable than Ni from the Sudbury soil samples studied,

suggesting that Cu may be more mobile. Alloway (1990) suggests that adsorption of heavy

metals to soil particles follows the order Cd < Ni < Co < Zn


Solonetzic soils (Spiers et al., 1984), a mechanism that may be very important in controlling

the effects of acid deposition on the soils of the Sudbury region. Secondary iron oxide

minerals, common in the orange coloured B-horizons of the Podzolic and Brunisolic soils of

the Sudbury region, have been described as important sinks for arsenic in Boreal soils of

Northern Alberta (Dudas et al., 1988).

An understanding of the clay mineralogy of regional soils is crucial. The secondary or

authigenic minerals of the clay fraction, when exposed to metal ions in the soil solution,

show ion exchange properties at their surface that are very important in controlling the

bioavailability of the soluble metal phases. On longer exposure not only is the surface of the

mineral particle involved, but the dissolved phase metal may penetrate the lattice layers or

tubes of these minerals, or exchange ions with the surface oxide layers. Once thus fixed in

the mineral structure, the metal ion cannot easily escape. Such processes must limit the

availability of the metal ions to the biota. Thus the soluble metal ion may be transformed

from a bioavailable free ion form into a bio-inert soil mineral complex.

Kodama (1979), in a literature survey of the clay mineralogical data of Canadian soils,

related the distribution of various clay fraction compositional assemblages to the soil-

physiographic regions of Canada. He indicated the subsoils of the Shield regions of Canada

to have a clay mineral assemblage dominated by clay mica, followed in order by mixed-layer

minerals, vermiculite, kaolinite and smectite. The smectite tended to be found in soils on the

western border of the Shield region, or in areas impacted by the draining of Glacial Lake

Agassiz. In 1993 clay mineralogical data from 461 publications were integrated with the Soil

Map of Canada to produce a clay mineralogical map for the surface soils of Canada at a 1:10

million scale (Kodama et al., 1993). Although the region of the Sudbury smelter footprint is

conspicuous by the absence of data, the clay mineralogy soils to the north of the region are

dominated by an admixture clay mica, chlorite and kaolinite. Bajc and Hall (2000) noted that

labile minerals such as sulphides and carbonates are slowly dissolved in a neutral to acid soil

environment, with the associated chemical constituents either removed in solution to the

water table, or scavenged locally by clay-sized phyllosilicates and secondary

oxides/hydroxides. Minor amounts of secondary carbonate minerals have been observed in


the finer textured subsoils immediately south of the abandoned Coniston smelter (Spiers,

personal observation).

Evans (1980, 1982) and Evans and Wilson (1985), in studies examining development of

podzolic soils west of the Sudbury region, documented presence of clay mica, chlorite and

kaolinite in the clay fraction of the loamy sand and sandy loam soils of the Chapleau area.

These studies, together with that of Jensen (1988), also provided extraction chemistry

evidence for presence of allophone and imogolite in the B-horizons of the Podzolic and

Brunisolic soils of the same area. Cruickshank et al., (1990), in micromorphological and

microchemical study of podzolic Ae and Bhf horizons documented the presence of carbon-

rich allophone-like layers encapsulating sand grains. The presence of a mineral with an

imogolite-like structure, observed with scanning electron microscopy and energy dispersive

spectroscopy, was also documented. As these latter studies have all been on soils formed on

similar parent materials in the same climate and vegetation zones as Sudbury, the presence of

the same inherited and authigenic clay mineral suite is probable in the soils of the Sudbury

smelter footprint.

Although there is no clay mineralogical data presented, Adamo et al., (2002) report the

content of the clay fraction as ranging from 30-209 g g-1 with a mean value of 109 g g-1 for

the soils studied in the Sudbury area, with the highest content of clay-sized particles in the

finer textured soils of the Copper Cliff area. Acidification in soil environments adjacent to

sulphur piles has been shown to dissolve chlorite, micaceous and smectitic minerals (Warren

and Dudas, 1992; Warren et al., 1993), a result possible in the study region with historic

emissions of sulphurous gases in the hundreds of thousands of tonnes from the Sudbury

smelters. The weathering of soil clay minerals also causes solubilization and translocation of

the dissolved trace metals released from the mineral structures.

Organic Horizons

The well to imperfectly drained undisturbed soils of the Sudbury region are characterized by

having organic (LFH) horizons ranging in thickness from 2 to 15 centimetres. The

designation LFH refers to the fresh plant detritus (L=litter) on the soil surface, the partially

decomposed organic layer (F=fermentation) and the well-decomposed organic layer


(H=humus). These poorly studied LFH horizons, initially composed almost entirely of

organic matter, are crucial sinks for the aerosolic particles (Spiers et al., 2002) from both

local and long-range sources, acting both as filters to prevent particle translocation to lower

horizons, and as exchange surfaces to absorb dissolved metals in precipitation and

throughflow. Colloidal soil organic matter, for example, strongly adsorbs Cu, Zn, Fe and

other transition metal ions, by acting as a chelating agent (Bohn et al., 2001).

In a study in the Falconbridge area, Golder Associates Ltd. (2001) reported total C content

ranges from a low of 0.16% to high of 10.1% in the 0-5 cm layer of the sampled soils. The

study documented carbonate contents to range below detection limit to a high of 0.89% in the

same 0-5 cm layer, with the higher levels being in areas which were either landscaped or

limed. Gundermann and Hutchinson (1995) reported that the organic C content of soils in the

0-5 cm layer in the Coniston smelter area decreased over the period between 1972 and 1992,

probably because of soil erosion. The latter study also reported a concomitant decrease in

water extractable metal content from 74, 33 and 52 g g-1 Ni, Cu, and Al to 2, 2, and 3 g g-

1, Ni, Cu and Al, respectively, suggesting that the decrease is strongly linked to the erosion

of surface organic matter. Hazlett et al., (1983) report organic C content of soils around the

Coniston smelter in the range 0.1% to 19.4%, with the high values being for the LFH

horizons and the lowest values for C-horizons. A recent study, for samples collected for the

0-20 cm layer from throughout the Sudbury region some 12 years ago, documented organic

carbon content ranges from about 0.5% to 2.1% (Adamo et al., 2002).

SOIL CHEMISTRY

Parent Materials

McKeague et al., (1979) compiled much of the published data in conjunction with their

studies of background levels of minor and trace elements in Canadian soils. They describe

levels for 53 profiles both on a national and regional basis. The mean levels ( g g-1)

documented are: Cr 43, Mn 520, Co 21, Ni 20, Cu 22, Zn 74, Sr 210, Hg 0.06, Pb 20. Their

data compare closely with data reported for levels in soils of the U.S.A. (Shacklette et al.,

1971). However, McKeague et al., (1979), with data for only 12 sites for the entire

Canadian Shield region, document no sites within the present study region, and base the


prediction of levels on a small sample base. Webb and Howarth (1979) point out that

extrapolation of the results of detailed studies from such type localities ignores the often

significant differences in composition within single stratigraphic formations that are

lithologically different in space.

Ginocchio et al., (2004), in a recent study describing micro-spatial variation in metal

contamination in the vicinity of a Chilean copper smelter, document a wide range of

variability in soil metal concentrations at the micro-site level having a dramatic influence on

plant recruitment. Such observations tend to temper the statement of Dudas and Pawluk

(1980) that predictions of elemental status of soil material can be based on average values of

parent rocks, even in glaciated terrains. Such prediction is complicated, even if the parent

lithology is uniform, by changes in composition owing to sedimentary source variations

and/or selective mobilization and redeposition of individual elements during weathering

processes (Webb and Howarth, 1979). Prediction of soil elemental status is further

compounded by the vagaries of glacial/fluvial/aeolian processes on surficial materials within

the Sudbury region.

The approach investigated by the U.S. Geological Survey, in conducting a reconnaissance

geochemical survey of Missouri State, was based on random sampling of previously mapped

broad geological, pedological, vegetational and hydrological units at different densities

(Tidball, 1978; Miesch, 1976; Erdmann et al., 1976). Analyses of variance were used to

study geochemical variation between each selected unit, and it was found, for many of the

30 to 40 analyzed elements, that significant differences occurred between the previously

mapped surficial units. These techniques were deemed suitable for regions containing

relatively homogeneous pedologic units, such as may be associated with glaciated terrain.

McKeague et al., (1979) used the data obtained in their compilation to calculate prediction

equations for minor elements based on more easily determined parameters such as clay, organic

C and the major elements (Al, Fe, Ca, Mg) as independent variables. They were able to account for

more than 50% of the variability of Mn, Cu, Pb, Co, Ni, Cr, Sr and Se in this for manner for

different sample groupings. Such relationships are obviously based on the ability of the

minor elements to proxy for the major elements in the crystal lattices of various minerals

(Dudas and Pawluk, 1980). They were able to predict Sr levels based on Ca alone for non-


calcareous samples, probably because Sr can proxy for Ca in plagioclase feldspars

(McKeague and Wolynetz, 1980).

Geochemical exploration work has produced a vast body of data in regions of known

mineralization, much of which is not pertinent to this study because the determinations are

made on a range of size fractions, rather than only


Cd, Cu, Pb and Zn as 3.95 ± 0.17, 0.67 ± 0.22, 26.07 ± 0.12, 52.5 ± 0.14, 79.74 ± 0.2,

respectively. These values are considerably higher than those documented by McKeague et

al., (1979), possible reflecting the inclusion of underlying metal-rich bedrocks in the

diamicton deposits forming the parent materials of the regional soils. The Geological Survey

of Canada completed a broad regional sampling and analytical program for much of Ontario

to approximately to lower half of the current study region as a component of a National

Geochemical mapping initiative in the 1990s (Garret, personal communication), with data

analysis and report publication currently in a preliminary stage only.

This brief overview has shown that, although there is a considerable amount of site-specific

data on levels of minor elements in soils in Canada, there are very few studies describing

regional variation of major, minor and trace elements. Studies relating concentrations of

specific elements to parent material variation are similarly sparse, and there is only one

detailed study of elemental partitioning among the various particle size fractions of soils,

although this does, admittedly, discuss the data with genetic overtones.

SUDBURY SOILS

McKeague et al. (1979) compiled much of the published data in conjunction with their

studies of background levels of minor and trace elements in Canadian soils, describing levels

for 53 profiles both on a national and regional basis (Table 2).


Table 2: Distribution of major and trace elements in Canadian soil parent materials.

Element Granite Shale Crustal

Abundance Canadian

Shield Soils Major elements %

Al 7.7 8.0 8.2 6.7

Ca 1.6 2.5 4.1 1.8

Fe 2.7 4.7 5.6 2.5

K 3.3 2.3 2.1 na

Mg 0.16 1.34 2.3 0.53

Na 2.8 0.66 2.4 na

Trace elements ( g/gm-1)

As na

Cr 4 100 100 19

Co 1 20 25 19

Cu 10 57 55 12

Mn 400 850 950 417

Ni < 1 95 75 12

P 700 770 1050 na

Pb 20 20 12.5 20

Se 0.18

S 285 450 375 409

V 20 130 135 na

Zn 40 80 70 57

(ng/gm-1)

Hg 107 Notes:

1) Values from Taylor (1964) 2) Values for soils from the Canadian Shield (McKeague, 1979)

They also document levels for surface horizons of Canadian soils which are similar in range

to those documented for surface soils worldwide, namely for Ni, Cu and As are 40 g g-1, 30-

20 g g-1 and 5 g g-1 respectively (Dreisinger, 1976; Alloway, 1990). Maximum values of

2300 g g-1 Ni for soil in the Sudbury area before the construction of the super stack, in

Copper Cliff, are documented as decreasing to 1715 g g-1 after the introduction of the super

stack (Dreisinger, 1976). For Cu, these values are essentially unchanged at 1750 g g-1 and

1738 g g-1, both results obtained from samples taken at Copper Cliff (Dreisinger, 1976).


Maximum pre-Super Stack S values of 0.38% were reported in samples from the Sudbury

area and maximum post-stack S values of 0.36% (Dreisinger, 1976). MOE acceptable level

for S in soil is 0.1% (Table 3; Heale, 1993). Iron levels in soils in the Sudbury region have

on the whole increased since the construction of the Super Stack from 4.7% up to 5.30%.

Zinc levels declined from 416 g g-1 to 313 g g-1, with a concomitant increase in As levels

from 50 g g-1 to 63 g g-1. These levels contrast greatly with maximum Cu and Ni values

reported by Taylor and Crowder (1983), 6912 g g-1, and 9372 g g-1, respectively, close to

the Copper Cliff smelter, decreasing with distance. The differences reported over time by the

above authors may merely reflect the natural site variability of the region, or be a product of

site micro-topographic variation which leads to micro-zones of enrichment because of snow-

melt or runoff translocation of aeolian materials.

Table 3: MOE guidelines for the upper normal limit for metals in Ontario soils (from Heale, 1993).

Parameter Soil (0-5 cm) Urban ( m/g dry weight) Rural ( m/g dry weight) As 20 10 B 15 10 Cd 4 3 or 4 Cr 50 50 Co 25 25 Cu 100 60 Fe (%) 3.5 3.5 Hg -- 0.5 Mg (%) -- 1 Mn 700 700/1000 Ni 60 60 Pb 500 150 Sb 8 1 Se 2 2 S (%) 0.1 0.1 V 70 70 Zn 500 500

The maximum values for NH4OAc extractable metals are Cu 2243 g g-1, Ni 6730 g g-1.

The maximum DTPA (diethylenetriaminepentaacetic acid) extractable metals are Cu 717 g

g-1, and Ni 1013 g g-1. Taylor and Crowder (1983) report that Cu and Ni concentrations in

wetland soil-sediment material are comparable to Sudbury area lake sediments (Semkin and

Kramer, 1976) and are comparable to concentrations measured in regional forest soils by

Freedman and Hutchinson (1980).

The 1978 the Ontario Ministry of the Environment (MOE) documented the guidelines for

maximum acceptable Ni, Cu, As and Co content in soils between pH 5.0 and 8.0 (0-10 cm


depth) at 100 g g-1 Ni, 100 g g-1 Cu, 25 g g-1 As and 25 g g-1 Co. Data collected from a

sparse sample set collected adjacent regional roads and highways in 1977 indicated that the

MOE guideline for surface soils were exceeded in an area of over 930 square kilometres for

Ni, 580 square miles for Cu, 65 square miles for As, and 43 square miles for Co (Heale,

1993), with no data being documented describing the soil pH. The information on analytical

procedures is not provided, but the data being reported as total concentrations of metals. As

the standard analytical procedure used by MOE is based on an aqua regia extraction of dried

and ground soil materials, the data cannot be described as total concentrations. By 1993

MOE guidelines for upper normal limits for heavy metal content of soils had been changed

as shown in Table 3 (Heale, 1993). In 1988 Ni levels in soil were up to 9 times background

level, As levels were 7 times greater than background levels, Cu levels were up to 14 times

above background levels (Heale, 1993), although the source for regional background

concentration data was not documented.

Hutchinson and Whitby (1974) describe the pH, electrical conductivity, LOI (loss on

ignition) and metal content of soil samples collected around the Coniston smelter impact

zone. The reported pH values ranged from 2.19 at 0.8 km from the smelter up to pH 3.39

about 50 km from the smelter on the surface. At 10 cm depth, pH ranged from 2.5 to 4.19 at

a distance of, 19.3 km, increasing to 3.42 about at 50 km. Generally, pH increased with depth

in the soil profile. Electrical conductivity decreased both with distance away from the

smelter and with depth in the soil profile.

The variability in LOI, whilst apparently showing no correlation with soil type, is probably a

function of increasing organic content away from the smelter and decreasing sulphur

compounds with distance. Hutchinson and Whitby (1974) also analyzed homogenized

samples taken from the upper 10 cm of soil for metal content by atomic absorption

spectrometry following digestion with a mixture of HF:H2SO4, with the digestate being

dissolved in HNO3 prior to analysis. The results indicated a trend of decreasing metal content

in soil with increased distance from the smelter (Table 4).

Adamo et al., (2002) analyzed pH of 20 samples collected from the east and northeast of the

3 Sudbury area smelters in 1992. They reported a mean pH of 4.5, which is within the range


(3.8-4.8) for unpolluted podzolic soils of the Sudbury area; however 40% of the samples had

a pH10 g g-1, which exceeds the OMOE (Negusanti and

McIlveen, 1990) guideline of 10 g g-1.

Adamo et al., (2002), using air-dried, crushed by hand and sieved soil samples from 0-20 cm

depth, analyzed for metal content by ICP-AES following acid digestion (HF/HNO3). A four-

step chemical extraction procedure (Singh et al., 1998; Ure et al., 1993) was also used to

fractionate the chemical forms of the heavy metals into the following fractions: 1) soluble

and exchangeable, 2) occluded in iron and manganese oxides, 3) organically bound or in the

form of sulphides, and 4) present mainly in mineral structures. These four fractions are

extractible with increasing difficulty: 1) easily extractible, 2) reducible, 3) oxidizable and 4)

residual. The concentration of Cu, Ni, Fe, Mn, Zn, Pb Cr and Cd in the various extracts was

determined by inductively coupled plasma atomic emission spectroscopy (ICP-AES), with

the analytical results summarized in Table 5.


Adamo et al., (2002) used scanning electron microscope (SEM) and energy dispersive X-ray

(EDS) spectroscopic analysis to examine the heavy mineral separate of the fine sand fraction

of the soils before and after sequential extraction treatments. Iron oxide and sulphide phases,

with associated Cr, Cu, Ni, Mn and Zn were associated with the Fe phases, with some iron

Table 5: Metal proportions in the various fractions from selected soils of the Sudbury region using the European Union extraction procedure.

HOAc Reducing Oxidizing Residue Mean Total

/ (% total metal)

Cu 27 17 26 31 433±474

Ni 2-46 2-24 2-20 17-92 410±410

Fe 0.1-2.2 7.9 2.8-14.7 85 2.6±0.85%

Mn 0.3-18.1 0.6-8.4 52 389±195

Zn 1.8-34.6 1.2-25.7 15.6 29.1-90 57±34.4

Pb 5 2.4-46.7 14 15.1-96.6 30±23.8

Cr 78.2-92-4 63±24

Cd 3.8 3.7 13.9% 2.7±0.8

Notes: Adamo et al. (2002)

oxide and sulphide particles being still visible after the various sequential extraction

procedures. The results suggested that some of the soil Cu may be in potentially more mobile

phases in the soils, with Ni being dominantly (average 64%) in the inorganic residual phase.

Unfortunately, detailed mineralogical examination of the various metal-rich phases was not

documented.

In an examination of regional surficial material geochemistry, Bajc and Hall (2000) noted

that concentrations of Cu and Ni in humus are significantly higher than concentrations in B-

and C-horizon soils, an observation supported by Spiers et al., (2002) (see Table 7).

However, Bajc and Hall (2000) attribute the higher content in the humus layer to the

scavenging and binding properties of fulvic and humic acids in complexing soluble airfall

metals, thus recognizing the possibility of anthropogenic sources being possibly responsible

for the elevated concentrations. Bajc and Hall (2000) report that the absolute concentration

of Cu in the B-horizon is lower than in the C-horizon, attributing the distribution to the

dissolution and hydromorphic dispersion under acidic soil conditions in the zone of

pedogenic weathering. Nickel shows a similar distribution in the horizons of the sampled


pedons (Bajc and Hall, 2000), suggestive of Ni being less affected by hydromorphic

processes. The authors do not attribute the differing distributions of Cu and Ni in the sola to

the different affinity of the elements to the mobile dissolved organic acids in the pedologic

system.

In analyzing the control of bedrock geology on humus-form chemistry, Bajc and Hall (2000)

noted only slight variations in the Ni and Cu ranges. However, definite trends were observed

in the B- and C-horizon data. The contents of Cu and Ni from samples collected over norite

and Levack gneiss were consistently higher than samples collected over other bedrock units.

The C-horizon also showed elevated Cu and Ni concentrations in samples collected over

quartz diorite and mafic extrusive rocks. The lower limit of concentration is similar to those

obtained from other bedrock domains.

Bajc and Hall (2000) sampled the pedogenic mineral horizons of soil profiles at several

geochemically anomalous sites to examine the vertical variation in Ni and Cu. The

postdepositional, low-temperature geochemical processes that occur in the porous and

permeable Quaternary sediments in an oxidizing environment may modify the chemistry of

mineral phases originally sorted into grain size fractions on the basis of resistance to glacial

abrasion. In an oxidizing environment, for example, fine carbonates and sulphide minerals

are dissolved (Bajc and Hall, 2000), with the dissolved products either translocated in

solution to be either reprecipitated in an authigenic phase, or absorbed by phyllosilicates and

secondary oxides/hydroxides. The translocation of the dissolved ions or ionic complexes may

result in elevated concentrations of the elements at depths. The samples from the Ae horizon,

the B- and C-horizons were size fractionated prior to analysis (Bajc and Hall, 2000), with


• The B-horizon is usually depleted in the elements present in the C-horizon, with the

depletion attributed to the destruction of labile minerals by oxidation and the

hydromorphic dispersion of the contained metals within the profile. There are some

instances where Ni is enriched in the B-horizon, usually coincident with an increase

in Fe in either the clay and/or silt and clay fraction.

• Concentration of elements generally increases downward through the C-horizon.

Bajc and Hall (2000) are not sure whether this is a primary or secondary signature.

• The proportion of Ni and Cu extracted with the hydroxylamine hydrochloric acid

leach in the –63 m fraction is quite high relative to that of the aqua regia digest.

This is indicative of a large proportion of Ni and Cu being potentially mobile in the

pedologic environment and not tightly bound as sulphide minerals.

The study provided data for mineral soil horizons only. The surface organic (LFH) horizons

were not sampled and analyzed.

Dudka et al., (1995) using ICP-AES (HNO3 and HClO4 acid digestion) present metal content

for 73 soil samples (Table 6). Gundermann and Hutchinson (1995) found concentrations of

Cu, Ni and H ions have decreased significantly in the surface soil horizons at the site of the

Coniston smelter, over the period, 1972-1992. As there was a concomitant reduction in the

organic carbon content in the soils over the same period, they suggested the reduction was a

result of surface horizon leaching and erosion, effectively removing metals from the top 5 cm

of the soil profile. Water extraction of metals indicated a high of 75 g g-1 Ni in 1972 and in

1992 this value was about 5 g g-1, together with about 30 g g-1 Cu in 1972 and in 1992

about 2 g g-1 Cu. Although the water extraction may be indicative of the bioavailability of

Ni and Cu, the values obtained cannot be readily compared to other regional studies because

of the variability in digestion methods.

Plants are the integrator of bioavailability of metals in soils, and various species have

different levels of tolerance for high levels of anthropogenic contaminant metals in soils.

Bowen (1966) documents, for example, normal levels of Ni and Cu in ve

metal levels in the soils of the sudbury smelter footprint€¦ · metal levels in the soils of the...

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